This invention relates to drilling apparatus and more particularly to valving mechanism that is mechanically forced to move axially outwardly through a bushing reduced diameter portion seat as the overshot coupling mechanism is moved to retract the latches.
U.S. Pat. No. 5,325,930 to Harrison discloses a toggle linkage movable to an overcenter position for locking the latches in a latch seated position and for retracting the latches.
U.S. Pat. No. 5,339,915 to Laporte et al discloses a one way retention valve in a core barrel inner tube assembly that functions to retain drilling liquid pressure in lost circulation situations resulting from, for example, drilling into a cavity or into a broken earth formation. However, with such apparatus, the descent in a drill string is very slow since the fluid bypass channel is blocked and liquid can not bypass except around the exterior of the latch body landing shoulder. Further, a heavy duty spring is used to create a high liquid pressure and retain a column of liquid above the core barrel inner tube assembly. This high pressure, in combination with pump surging, has resulted in wear on the valve ball seat. The ball essentially hammers the seat which, over a period of time, damages the seat. Also, spring pressure has to be constantly adjusted to compensate for wear and the adjustment affects the gap between the core lifter and bit.
U.S. Pat. No. 5,020,612 to Williams discloses a core barrel inner tube assembly having a resilient ring (bushing) in the fluid bypass channel through which a valve ball is forced inwardly by fluid under pressure when the inner tube assembly is in its core collecting position at the bit end of the drill string.
U.S. Pat. No. 3,333,647 to Karich et al discloses a core barrel inner tube assembly having spring mechanism acting between a latch body and a latch release tube to constantly urge the latch release tube to a position permitting the latches moving to a latch seated position.
In order to make improvements in valving mechanism operable in a fluid bypass channel that bypasses the latch body landing shoulder of drilling apparatus and controls the head of fluid axially outwardly of the bypass channel, this invention has been made.
In United States Patent application Ser. No. 08/802,557, now U.S. Pat. No. 5,904,393 there is disclosed a resilient valve seat in a fluid bypass channel in a core barrel inner tube assembly wherein a valve ball is forced axially inwardly through the seat by fluid under pressure and resiliently urged outwardly toward the valve seat after having passed through it to maintain at least a minimum fluid pressure head in the drill string. However, at times in bore holes in which there is a very low water table and the valving assembly retains a large column of water in the drill string relative to the water table level exterior of the drill string, it is difficult to pull the core barrel inner tube assembly outwardly of the inner end of the drill string.
In order to make improvements in valving mechanism in a fluid bypass channel that bypasses the latch body landing shoulder of drilling apparatus and controls the head of fluid axially outwardly of the bypass channel, this invention has been made.